For those unwilling to accept the risk associated with buying a single company’s shares, the primary selections on the menu are a couple of exchange-traded funds (ETFs) that track solar indexes, and a recently issued corporate bond. Nonetheless, even the ETFs — occasionally buffeted by energy prices as well as the price of photovoltaic (PV) cells — pose plenty of volatility.

In recent decades, the chief means for consumers looking to invest in solar has been to install an array of solar photovoltaic collectors on the roof of their home. The cost, which easily can run into the tens of thousands of dollars, includes the associated electronic controls and metering equipment needed to store the energy and return any unused excess power to the grid for a rebate from the local utility.

Although there are a number of “green” funds or “alternative energy” mutual funds, these tend to invest in companies that make a broad array of environmentally friendly, energy-s